Channel and Transmission Scheme Modelling
for Radio Local Loop and Powerline Communication Systems
Topic:
Radio Local Loop and Powerline Communication Systems
Figure 1: LMDS as a possible RLL scenario
Abstract:
To improve the conveyance of broadband services
such as data, Internet, voice, video and multimedia between users'
premises and a broadband core network, it is necessary to ascertain
the performance of different access and transmission systems. In
this thesis, technologies of data transmission in Asynchronous
Transfer Modus (ATM) for the local loop are examined, using
either the line-of-sight radio channel at about 28 to 30 GHz
or the powerline wired access. As an example, a Local
Multipoint Distribution Service (LMDS) system proposal is
evaluated, considering data coding for error protection, high-gain
antenna technologies, and a channel adapted transmission scheme. The
system design contains a Reed-Solomon coder, multiple rates
convolutional codes, interleaver, and either 16 QAM or QPSK
modulation. The QPSK modulation works in connection with the
convolutional codes with code rate 1/2 which increases
up to 7/8 through puncturing. The coding process is
simulated separately to evaluate its performance.
In all simulations an accurate modeling of the physical layer and
the transmission technologies is performed. The Wireless ATM
(WATM) simulator currently contains a Gilbert-Elliott channel
model to simulate packet errors due to radio propagation loss. This
model is improved and parameterized according to the radio channel
and powerline measurements respectively, and the results of the
system coding and modulation simulations. The error correcting codes
evaluation needs a channel model considering the measurement results
as well. The signal propagation effects due to noise, distance-related
attenuation, fading, multipath propagation, reflections, and weather
influence are considered by means of the models generating different
error characteristics.
The results can be used in different simulations to adapt the
protocols for WATM and Dynamic Channel Allocation (DCA) to
local loop and powerline characteristics. For a complete cellular
system evaluation with the MADCAT simulator according to the
Carrier to Interference (C/I) ratio on the current link
caused by multiple participants and noise the transmission scheme
characteristics are considered as well.
